1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing apparatus, and especially relates to a substrate processing method and a substrate processing apparatus for stripping from a substrate a resist used as a mask for an ion implantation.
2. Description of Related Art
In a manufacturing process of a semiconductor device, impurities (ions) may be implanted into a specific region of a surface of a substrate such as a semiconductor wafer. For example, phosphorus ions, arsenic ions, and boron ions are used as the impurities. A resist is provided on the substrate to implant ions only into a desired region of the substrate. The resist is formed of photosensitive resin, for example. A region other than the desired region is masked by the resist. After ion implantation, the resist is removed from the substrate.
A method using ashing is known as a method of removing the resist from the substrate. In the method, an ashing apparatus ashes the resist on the substrate. After that, the substrate is carried in a cleaning apparatus, and residues (polymer) of the resist, are removed from the substrate in the cleaning apparatus. The ashing is carried out by using plasma. The plasma sometimes damages a region, of the surface of the substrate, which is not covered by the resist.
In order to prevent the damage to the substrate, it is considered that the plasma ashing is performed at a mild condition and the substrate is cleaned with a stripping liquid to remove the resist after the plasma ashing. The stripping liquid is, for example, SPM (sulfuric acid/hydrogen peroxide mixture) which is a mixed liquid of sulfuric acid and hydrogen peroxide solution.
As related art, Japanese Laid Open Patent Applications JP-P2001-156049A and JP-P2002-110605A disclose cleaning of a substrate by using ozone water.
When the condition of the plasma ashing is mild, the process time of cleaning will be substantially long. For this reason, it is desired to shorten the cleaning time.
As related art, Japanese Laid Open Patent Application JP-P2004-96055A discloses supplying hot water to a surface of a substrate before removing organic matter from the surface of the substrate.
Meanwhile, a cured layer is formed in a surface of a resist when the resist is used as a mask for an ion implantation. The cured layer is hard to be stripped, thereby it take long time to strip the resist by using a stripping liquid.
Japanese Laid Open Patent Applications JP-P2004-327537A and JP-P2007-334689A disclose methods to facilitate a stripping of a resist by destroying a cured layer of the resist.
However, the present inventor recognizes that when a cured layer of a resist is physically destroyed by using the methods disclosed in Japanese Laid Open Patent Applications JP-P2004-327537A and JP-P2007-134689A, a region of a surface of a substrate, which is covered by the resist, may also be destroyed.
FIG. 1 shows a substrate 80 on which a resist 84 and gate electrodes 82 are formed. The gate electrodes 82 are structures having high aspect ratio and are not covered by the resist 84. The substrate 80 is a semiconductor wafer. The present inventor recognizes that when an impact to destroy the resist 84 is applied, the gate electrodes 82 may be destroyed.